冷冻电子显微镜技术进展及环境研究应用

Progress and Environmental Research Applications of Cryo-Electron Microscopy

电子显微镜是表征微观粒子结构的必要手段,但预处理过程会对含水样品结构造成破坏,导致结果失真.冷冻电子显微镜(Cryo-EM)技术通过将样品在低温下快速冷冻,使水合样品处于无定形玻璃态冰层内,在保障高真空度要求的同时减少电子辐射对样品的破坏,目前已成为高分辨地观察含水样品原始状态下结构最先进的手段,在生物、材料等领域应用广泛.本综述总结了冷冻电镜在电子元件、成像技术与分辨率等方面的进展,综述了样品制备方法及三维重构技术.鉴于绝大多数环境样品为含水样品,冷冻电镜技术在大气、水体、土壤等环境介质中的应用扩宽和深化了对环境中微纳米粒子本身形态结构和粒子间相互作用关系的理解.我们期待冷冻电镜为环境科学研究带来突破性贡献.

Electron microscopy(EM)is one of the most important techniques to characterize the morphology and structure of micro-and nano-particles.However,conventional procedures for sample preparation often alter the structure and morphology of samples with high water contents,causing distortions and misinterpretations for EM characterizations.The invention of Cryo-electron microscopy(Cryo-EM)has largely solved this problem.Via rapidly freezing the hydrated samples at low temperatures,cryogenic techniques instantaneously transform liquid water into amorphous ice to ensure high vacuum and reduce electron radiation damage,allowing researchers to observe hydrated samples in their native state with high resolution.For example,applications of Cryo-EM during the COVID-19 pandemic have demonstrated the amazing ability of Cryo-EM to visualize the detailed structure of SARS-CoV-2 viruses,which provides vital knowledge for rapid and reliable detection and diagnosis of the disease,transmission mitigation,and vaccine development.So far,Cryo-EM technology has been widely used in materials,biology,pharmaceuticals,and other fields of research,successfully broadening and deepening the understanding of the interactions between micro-and nano-particles.This review summarizes the recent development of Cryo-EM from aspects of electronic components,imaging technology,and resolution and introduces the sample preparation methods.Furthermore,the three-dimensional reconstruction method is highlighted to advance the EM method from 2D to 3D.As most environmental samples are highly hydrated,Cryo-EM will likely become an essential tool to investigate microscopic particles in the environmental field.This review gives examples of the applications of Cryo-EM in the formation of aerosol particles in the atmosphere,observing biofilm morphology in the water treatment process,the pore structure of activated sludge flocs,and the potential mechanism of soil microorganisms on heavy metal remediation.Finally,the prospects of Cryo-EM are summarized and discussed.We expect that with software,hardware,and artificial intelligence development,Cryo-EM technology can achieve faster data acquisition and higher resolution and make breakthrough contributions to environmental chemistry research.